This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Netherlands is constructing fish passes to make rivers and streams accessible to fish again. But how effective are these structures?
New Ph.D. research by Panos Panagiotopoulos of Wageningen University shows that successful fish migration requires more than making individual barriers passable. Maintenance and water management are also crucial. Weirs, dams and other barriers make it difficult for fish to move through rivers and streams.
Many fish species need to migrate to find food, reproduce or reach suitable habitats. Panagiotopoulos investigated how effective fish passes are and what is needed to restore connections between fish habitats. To do this, he analyzed data from fish passes, studied fish movements in the River Vecht and examined the influence of management, maintenance and changing environmental conditions.
Panagiotopoulos analyzed data from 82 fish passes across Dutch rivers and streams. Of the 38 native fish species found in the surrounding areas, 35 were also recorded in fish passes. Which species were recorded varied between fish passes.
The timing and duration of monitoring also proved to have an influence. "When designing and evaluating fish passes, we often focus on particular target species. But smaller fish and species that are less capable swimmers also need to be able to move through our rivers," explains Panagiotopoulos.
"If we want to restore biodiversity, we need to consider the entire fish community." A second study focused on the River Vecht in the province of Overijssel. Here, Panagiotopoulos studied the movements of three fish species over five years: sea trout, ide and burbot. Along the migration route studied are 11 successive weirs with fish passes or bypass channels.
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